7809 IC Is Getting Super Hot on the UD 2.7 rev. C

[ItsChloeUwU]

Hi,
so, the problem is.. i got this UD 2.7 rev. C from a guy on facebook years ago...
I just now found it in a box when i moved and i tryed to power it up as show in the pic with a 18V 20va (10va x2 in parallel) in the ac input.

i didn't touch anything or attached anything to it.. and after some minutes (i was ready to start probeing it with the oscilloscope) it started heating up the 7809 IC so much.

I never even tryed to get into this kind of things with the UD 2.7 rev. C or any other controller for DRSSTC's... but since i'm tying to learn and mature a bit of confidence from working with oscilloscopes and circuits in general before attempting a DRSSTC i was wondering if i'm doing all righty... do i have to add some resistor somewhere or do i need to attach a load somewhere as i read online to avoid something like this from happening or is it just a problem with the UD 2.7 rev. C it self?

Did i got a broken one or is it only the IC or what? it sould be a voltage regulator if im not mistaken... so i wonder why is getting so hot.. i readed online that the rev A and B had this issue... maybe it's the wrong component? i saw that now it sould be the rectangular black one.. not this one with the heatsink to attach to it...

Also.. please if u guys could kindly guide me trough how to check if the driver is working would be amazing... i got an oscilloscope... and it has a square wave generator of 1Khz... i also did a suqare wave generator with a potentiometer for the amplitude to change if its useful.. it sould be something like 10 to 100Khz if im not mistaken..
And i have some resistors laying around... i also have a GDT that im working on and i guess thats it.. ofc i have a tester too. THX a lotty for your help!

Childish pic for explanation  (sorry about the bad edit but i was in a rush):

[klugesmith]

A search for UD2.7 popped up loneocean's page with a picture that shows a heat sink on that part.
The need for heatsink (or not) and the normal temperature without a heatsink depend on the circuit design, not on whether you got an inferior copy of "7809 voltage regulator in TO-220 package".

What are your voltages at output of rectifier, output of 24 V regulator, output of 9 V regulator, and output of 5 V regulator?
I would call out reference designators like C1, but they might not be standard between makers of the board.
Even the schematic on loneocean's page looks pasted together, with three different symbols for 78xx regulators. And three different  arrow symbols for power net connections, etc.

[edit] on further investigation, loneoceans' Rev C schematic has a switching regulator module in that place.   Device type R-789.0-0.5, reference designator R7809 (instead of U-something or IC-something). It's right there in bill of materials: https://www.loneoceans.com/labs/ud27/UD2_7%20REV%20C_BOM.pdf
I'm unfamilar with these devices, and UD boards, but would NOT assume that it's interchangeable with a LM7809 linear voltage regulator.  Need to look it up.  The LM7809 may have been around since before your parents were born.

I bet the UD board design was revised, replacing linear LM7809 with the RECOM switcher, to solve an overheating problem.  The regulator drops 15 volts.  With even 0.1 amp load the linear part would dissipate 1.5 watts, and get "super hot" if used without a heatsink or forced air cooling.   If you have a linear part there, I bet you can move ahead after putting a proper heat sink on it.

[flyingperson23]

Yes, the 9v regulator definitely needs a heatsink. The 5v might also get warm.

[verliebt_in_neukölln17]

I've had this exact same issure when starting out, make sure that your ICs are in their right places and you haven't swapped any around on accident, especially the 74hc____ ICs because I screwed up once and that lead to the 9v regulator almost desoldering itself off the board.

Though at the end of the day I recommend you getting a 9V DC-DC converter because they are honestly just better at not generating heat, most also come with the exact pin layout.